THE THEORY OF ENERGY AND THE LIVING WORLD. 527 



the vital principle exterior to the living being, independent of its sub- 

 stance, bonded to it temporarily, working, it might be said, with human 

 hands, and accomplishing the deeds and actions of life, and at last 

 quitting the body which had served as its hostelry, not perhaps under 

 the form of a butterfly, the graceful genius of the Greeks, but in a man- 

 ner equally real if less visible. The vitalists of the middle ages, like 

 Paracelsus and Van Helmont, had divided up this principle of life into 

 subordinate principles, and multiplied these personifications under the 

 name of arches. Some trace of them may be discovered in the vital 

 properties of Bichat and others of the moderns, phantoms which CI. 

 Bernard loved to compare to the nymphs, dryads, and sylvans of 

 mythology. 



In the face of physicians and philosophers who explained the phe- 

 nomena of life as the liberated activity of a vital principle, distinct or 

 not from the thinking soul, arose an adverse system, the mechanical. 

 The scientific spirit has evinced in all epochs a lively predilection for 

 this doctrine, and in our day it has finished by adopting it and con- 

 founding the other. A single order of things now embraces life and 

 the physical phenomena, for all the phenomena of the universe reduce 

 to an identical mechanism, and are represented by the atoms and their 

 motion. This conception of the world which the philosophers of the 

 Ionic school had originated in remote antiquity, and which Descartes 

 and Leibnitz later had modified, has come down to us under the name 

 of the kinetic theory. The mechanism of atoms, ponderable or impon- 

 derable, contains the explanation of all phenomena. Physical properties 

 and the manifestations of life, the whole world even, offers nothing in the 

 last analysis but motion. All phenomena are expressed by an atomic 

 integral, and in this we find the majestic unity which dominates modern 

 physics. The forces of life can not be distinguished in their ultimate 

 examination from other natural forces; all are confounded in molecular 

 mechanics. 



Without arguing the philosophical value of this doctrine, which 

 indeed has justified its sway over physical sciences by the discoveries 

 to which it has given rise, it may be observed that it has been of small 

 aid in biology. It is precisely because it descends too profoundly to 

 the root of the thing and that it is analytic to the last degree that it 

 ceases to explain. The step is too far from the hypothetical atom to 

 the apparent and concrete facts for the former to assist in accounting 

 for the latter. The taugible vital phenomena lose their proper appear- 

 ance, and can no longer be recognized in their traits, either specific or 

 universal. 



On the other hand, the theory of energy conduces to a conception 

 quite as general, but at the same time more sure, more comprehensive, 

 and sufficiently near the reality to be translated into facts, and contin- 

 ually to acquire new vigor. Its introduction in biology dates but from 

 yesterday as it were, but it has already taken a considerable place and 



